A pitch control system is typically used to adjust the pitch of one or more rotor blades of a wind turbine. As is generally understood, the pitch control system may include a motor that is configured to rotate a rotor blade to a desired pitch angle to adjust an amount of wind energy captured by the blade.
Known pitch control systems typically use a direct current (DC) motor that has a series field winding to pitch the blades. Such DC motors may include a dynamic braking resistor to facilitate absorbing excess energy generated by the DC motor during motor braking conditions. Moreover, to reverse a rotational direction of the DC motor, rectification diodes are included in the pitch control system. Such dynamic braking resistors and rectification diodes may add cost and complexity to known pitch control systems and may produce energy losses within the pitch control system. Further, the series field winding of the DC motor typically shares a current with an armature of the DC motor, which can be increased or decreased to adjust the operation of the DC motor. However, due to the common current between the armature and the winding, an adjustment of the armature current will also affect the winding current. As such, independent control of the armature and the winding of the DC motor may not be possible.
Typically, electrical power is supplied to the DC motor and the various other electrical components of the pitch control system via an electric utility grid. As a result, when the electric utility grid experiences a high voltage event or transient, the pitch control system may be subject to voltages that exceed the grid's nominal grid voltage. Such high voltage transients may lead to damage to the DC motor and/or other electrical components of the pitch control system, particularly when the voltage transient lasts for extended period of time and/or when the grid voltage greatly exceeds the nominal grid voltage.
Accordingly, an improved pitch control system that is capable of accommodating high voltage transients would be welcomed in the technology.